JP2005250089A - Imaging lens and manufacturing method of the lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging lens with which a diaphragm by a light shielding pattern is accurately formed on the surface of the lens with high dimensional accuracy and improvements in flare and size or the like are realized compared with a conventional lens. <P>SOLUTION: A surface S2 is provided with a translucent region 10 which is made translucent to an incident luminous flux, a light shielding region 20 which shields the incident luminous flux and a difference in level 30 which is made along the normal direction of the surface S2 to define the boundary of the translucent region 10 and the light shielding region 20. An aperture diaphragm having a more precise dimension is easily obtained by forming a coating film having a light shielding capability over the entire region 20 using the difference in level 30 as a boundary. Thus, generation of flare and ghost is suppressed while the size is reduced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an imaging lens suitable for mounting on a relatively small imaging device, and a method of manufacturing a lens constituting the imaging lens.

  In general, an imaging lens mounted on an imaging apparatus such as a silver salt camera, a digital camera, or a video camera includes a diaphragm as a light shielding unit that blocks a part of an incident light beam at one or a plurality of locations. Examples of the diaphragm include an aperture diaphragm that defines the intensity of the light collecting power and a field diaphragm that defines the field of view. The aperture stop, also called an iris stop or brightness stop, limits the diameter of the on-axis light beam that allows it to pass through the lens and functions to adjust brightness, resolution, or contrast. On the other hand, the field stop functions to limit the field that can be used in terms of imaging performance, and to form a sharp edge with respect to the field to define the size and shape of the image. In addition to the aperture stop and field stop described above, there are also stops for preventing flare and ghost. This is generally called a flare cut stop. Hereinafter, lenses having a function of limiting an incident light beam in a lens system are collectively referred to simply as “aperture”.

Usually, these diaphragms, particularly the aperture diaphragm, are constituted by mechanical parts, and are constituted as separate parts from the lens. In many cases, the field stop and the flare cut stop are also composed of a mask member that is a separate component from the lens. On the other hand, for example, Patent Documents 1 and 2 propose a method for realizing the function of a flare-cut stop without separately providing a mask member. Patent Document 1 describes an invention relating to an objective lens in which a light-shielding pattern as a flare cut stop is formed by direct printing or painting on a lens surface. Patent Document 2 describes an invention relating to a projection-type television apparatus that includes a projection lens having a light-shielding pattern printed as a flare-cut stop on a lens surface.
Japanese Utility Model Publication No. 6-64218 Japanese Patent No. 2507166

  By the way, since the imaging apparatus as described above has been remarkably compact in recent years, the lens system has also been miniaturized, and the overall length and outer diameter thereof have been reduced. In particular, an imaging lens of an image input module camera (simply referred to as a portable camera) mounted on a mobile phone or the like that is rapidly spreading is extremely small. In such an imaging lens of a portable camera, the diameter of the incident light beam is extremely thin, so that the thickness of the member constituting the diaphragm is relatively larger than the diameter of the incident light beam compared to a normal imaging lens, Flares and ghosts are likely to occur due to reflection at the end face of the opening. In particular, in the case of an imaging lens that has been downsized in recent years, the thickness of a mechanical member such as an aperture stop cannot be ignored from the viewpoint of downsizing.

  On the other hand, an aperture stop in an imaging lens such as a portable camera is often a fixed stop from the viewpoint of simplifying the configuration. Therefore, instead of the mechanical diaphragm member, it is conceivable that the fixed diaphragm as a whole that prevents miniaturization or causes flare or the like is configured with a light shielding pattern as described in Patent Documents 1 and 2. In this case, without using a diaphragm member, a light-shielding paint or the like is directly applied to the lens surface and drawn so as to have a predetermined shape to form a light-shielding pattern that serves as a diaphragm, thereby suppressing the occurrence of flare and ghost. it can. Further, since no diaphragm member is used, it can contribute to downsizing.

  However, the imaging lens of a portable camera is increasingly miniaturized. For this reason, when directly printing or applying a light-shielding paint or the like on the lens surface, it is becoming difficult to accurately form a light-shielding pattern, which may cause a problem in terms of manufacturability. Note that the inventions described in Patent Documents 1 and 2 are intended for relatively large lens systems such as single-lens reflex cameras and projection lenses compared to portable cameras and the like, and are specific to the above-described small imaging lenses. The problem is not specifically considered.

  The present invention has been made in view of such a problem, and an object of the present invention is to form a diaphragm with a light-shielding pattern accurately on the lens surface with high dimensional accuracy, and to improve flare, reduce size, etc. compared to the conventional art. It is an object of the present invention to provide an imaging lens that can be manufactured and a lens manufacturing method that can easily manufacture a lens that constitutes the imaging lens.

  The imaging lens according to the present invention is an imaging lens composed of a single lens or a plurality of lenses, and at least one lens surface of the single lens or the plurality of lenses blocks a light-transmitting region that transmits the incident light beam and the incident light beam. A light-shielding region and a step in the normal direction of the lens surface that defines the boundary between the light-transmitting region and the light-shielding region, and a coating film having a light-shielding property is formed on the entire light-shielding region with the step as a boundary. It is.

  A method of manufacturing a lens according to the present invention is a method of manufacturing a lens having a light-transmitting region that transmits an incident light beam and a light-blocking region that blocks the incident light beam, and the light-transmitting region and the light-shielding region are in the normal direction of the lens surface. After providing a step defining the boundary with the region, a coating film having a light shielding property is formed over the entire light shielding region with the step as a boundary.

  In the imaging lens according to the present invention, since there is a step in the normal direction of the lens surface that defines the boundary between the light-transmitting region and the light-shielding region, an aperture having a highly accurate aperture defined by the step can be obtained. .

  In the imaging lens according to the present invention, the entire light shielding region of the lens surface may have a shape that protrudes in a normal direction with respect to the lens surface of the light transmitting region with a step as a boundary, or a concave shape. A convex portion or a depressed concave portion protruding in the normal direction with respect to the lens surface of the light transmitting region may be formed in a part of the light shielding region, and a step may be formed by the convex portion or the concave portion. Further, the light shielding region can function as an aperture stop.

  According to the imaging lens of the present invention, the imaging lens includes a lens or a plurality of lenses, and at least one lens surface of the single lens or the plurality of lenses blocks a light-transmitting region that transmits the incident light beam and the incident light beam. And a step in the normal direction of the lens surface that defines the boundary between the light-transmitting region and the light-shielding region, and a coating film having a light-shielding property is formed on the entire light-shielding region with the step as a boundary. Therefore, it is possible to obtain a diaphragm having a sufficiently thin thickness and a highly accurate opening defined by the step. Thereby, generation | occurrence | production of a flare and a ghost can be suppressed, aiming at size reduction.

  According to the lens manufacturing method of the present invention, after providing a step defining the boundary between the light-transmitting region and the light-shielding region in the normal direction of the lens surface, the light-shielding coating film is shielded from light using the step as a boundary. Since it is formed over the entire region, it is possible to obtain a diaphragm having a sufficiently thin thickness and a highly accurate opening defined by a step. Thereby, generation | occurrence | production of a flare and a ghost can be suppressed, aiming at size reduction.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a configuration example of an imaging lens according to an embodiment of the present invention. Symbol Si indicates the i-th lens surface from the object side.

  The imaging lens shown in FIG. 1 is mounted and used in, for example, a portable module camera or a digital camera using an imaging element such as a CCD (Charged Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). Is. This imaging lens has a configuration in which a first lens L1, a second lens L2, and a third lens L3 are sequentially arranged from the object side along the optical axis Z1. An imaging element such as a CCD (not shown) is disposed on the imaging surface (imaging surface) of the imaging lens. A cover glass CG for protecting the imaging surface is disposed near the imaging surface of the CCD. Furthermore, in addition to the cover glass CG, other optical components such as an infrared cut filter and a low-pass filter may be disposed between the third lens L3 and the imaging surface (imaging surface). Here, the image side surface S8 of the cover glass CG coincides with the imaging surface (imaging surface) of the imaging lens.

  The first lens L1 has a planoconvex shape with a convex surface facing the object side in the vicinity of the paraxial axis, and has positive power. The object-side surface S1 may be aspherical. The second lens G2 has a meniscus shape in which the object-side surface S3 is concave on the object side, and has negative power, for example. Further, at least one of the surface S3 and the surface S4 may be aspherical. The third lens L3 has, for example, a positive meniscus shape in which both surfaces are aspherical and the shape near the paraxial is convex on the object side.

  In the imaging lens, at least one lens surface of the first to third lenses L1 to L3 continuously surrounds the light-transmitting region that transmits the incident light beam, and the periphery of the incident light beam. And a step in the normal direction of the lens surface that defines the boundary between the light transmission region and the light shielding region. This will be specifically described below.

  FIG. 2A shows a detailed configuration of the first lens L1 shown in FIG. FIG. 2B is a plan view viewed from an arrow direction II (B) in FIG. As shown in FIGS. 2A and 2B, the image-side surface S <b> 2 of the first lens L <b> 1 has a circular light-transmitting region 10 centered on the optical axis Z <b> 1 and an annular shape surrounding the light-transmitting region 10. And a step 30 that defines the boundary between the light-transmitting region 10 and the light-shielding region 20. In the light shielding region 20, a coating film having a light shielding property is formed. Examples of the material used for the coating film include black lacquer paint. The height (gap) of the step 30 in the normal direction of the surface S2 is preferably about 0.05 mm to 0.1 mm. The light shielding region 20 is a convex portion with the step 30 as a boundary and projecting further toward the image side than the light transmitting region 10 in the normal direction of the surface S2. Thereby, a coating film can be formed only on the light shielding region 20 relatively easily without being applied to the light transmitting region 10. The light shielding region 20 functions as an aperture stop that blocks the peripheral edge of the incident light beam from exiting from the surface S2. The first lens L1 may be made of optical glass or may be made of a plastic material. However, it is desirable that the surface S2 is made of a plastic material from the viewpoint of ease of processing.

  The first lens L1 of the imaging lens configured as described above is provided with a step 30 that defines the boundary between the light-transmitting region 10 and the light-shielding region 20 in the normal direction of the surface S2. As described above, a light-shielding coating film is formed over the entire light-shielding region 20.

  Next, operations and effects of the imaging lens configured as described above will be described.

  In the imaging lens of the present embodiment, as shown in FIG. 1, the incident light incident on the surface S1 of the first lens L1 from the object side is blocked by the light shielding region 20 on the surface S2. The light emitted from the light transmitting region 10 without being blocked by the light shielding region 20 is converged toward the second lens L2. Here, by passing through the surface S2, the axial light beam diameter is limited without causing flare or ghost, and adjustments such as brightness, resolution, or contrast are performed. The light emitted from the light transmitting region 10 passes through the second lens L2, and travels toward the third lens L3 while diverging. The light transmitted through the second lens L2 is further transmitted through the third lens L3, and converges on the imaging surface (S8) through the image side surface S6.

  As described above, according to the imaging lens of the present embodiment, the step 30 in the normal direction of the surface S2 that defines the boundary between the light transmitting region 10 and the light shielding region 20 is provided in advance on the surface S2. As compared with the case where no step is provided, an aperture stop having a more accurate dimension can be easily formed. In other words, the lens surface is processed in advance to form a step with high precision compared to the case where the aperture stop is formed by patterning a coating film having an opening of a predetermined shape directly on a lens surface without a step. Therefore, it is possible to form an aperture stop having a high accuracy using this step. Further, since the light shielding region 20 is provided directly on the surface S2, the total number of parts can be reduced compared to the case where an aperture stop is provided as a separate optical member, which is advantageous for downsizing and cost reduction. . Furthermore, since a sufficiently thin coating film can be formed in the light shielding region 20, the occurrence of flare and ghost due to reflection at the opening end face of the aperture stop is suppressed, and a good image can be obtained. Further, the vignetting of the peripheral light flux at the aperture end face of the aperture stop is eliminated, and the peripheral light amount ratio is improved.

  Although the present invention has been described with reference to the embodiment, the present invention is not limited to the embodiment, and various modifications can be made. For example, in the present embodiment, the light shielding area is formed of a convex portion protruding from the light transmitting area in the normal direction of the lens surface. On the contrary, the light shielding area is the normal line of the lens surface. It can also comprise so that it may consist of the recessed part depressed in the direction rather than the translucent area | region. Specifically, as in the first modified example (modified example 1) illustrated in FIG. 3, the surface S2 has a light shielding region 20 that is recessed from the light transmitting region 10 in the normal direction of the surface S2. May be.

  Further, in the present embodiment, the entire light shielding region is formed of a convex portion protruding from the light transmitting region. However, a part of the light shielding region has a convex portion protruding so as to surround the light transmitting region. May be formed. Specifically, as in the second modified example (modified example 2) shown in FIGS. 4A and 4B, a part of the light shielding region 20 of the surface S2 goes around the optical axis Z1 as a central axis. In addition, the projection 21 may protrude from the light shielding region 10 in the normal direction of the surface S2. Here, the convex portion 21 forms a step 30 that defines the boundary between the light transmitting region 10 and the light shielding region 20. 4A and 4B correspond to FIGS. 2A and 2B, respectively. Alternatively, as in the third modified example (modified example 3) illustrated in FIG. 5, a part of the light shielding region 20 on the surface S2 circulates around the optical axis Z1 as a central axis and is shielded in the normal direction of the surface S2. You may make it have the recessed part 22 depressed rather than the area | region 10. FIG. In this case, the recess 22 forms a step 30 that defines the boundary between the light transmitting region 10 and the light shielding region 20. Even with the configurations as in the first to third modifications described above, it is possible to easily realize a diaphragm having a more accurate dimension than in the case where no step is provided.

  In the present embodiment, the case where the light shielding region functions as an aperture stop that blocks the peripheral edge of the incident light beam has been described. However, the present invention is not limited to this. For example, as in the fourth modified example (modified example 4) shown in FIG. 6, the light shielding region 20A that functions as a field stop may be formed on a predetermined lens surface. In this case, the predetermined lens surface defines a light-transmitting area 10A that is approximately rectangular with the optical axis as the center, a light-shielding area 20A that surrounds the light-transmitting area 10A, and a boundary between the light-transmitting area 10A and the light-shielding area 20A. And a step 30A. A coating film having light shielding properties is formed over the entire light shielding region 20A. The light shielding region 20A defines an imaging range and functions to block excess light outside the imaging range from entering the imaging device. Note that the outline shape of the translucent region 10A is not limited to that shown in FIG. Furthermore, the present invention is applicable to all diaphragms that limit incident light flux, such as flare-cut diaphragms. Further, the present invention can be applied not only when the light shielding region continuously surrounds the entire periphery of the light transmitting region but also when a discontinuous light shielding region is formed.

  Further, the lens surface on which the light shielding region and the light transmitting region whose boundaries are defined by the steps is provided may be a spherical lens or an aspherical lens. In the above embodiment, the case where the imaging lens has three lenses has been described. However, the present invention is not limited to this. A single lens may be used, or two lenses or four or more lenses may be used.

  Moreover, as a material used for the coating film formed in the light shielding region, any paint other than the lacquer paint can be used as long as it has a light shielding property and can be applied to the lens surface. The coating film may not be black.

It is sectional drawing showing the example of 1 structure of the imaging lens which concerns on one embodiment of this invention. It is sectional drawing and the top view showing the principal part structure of the imaging lens shown in FIG. It is sectional drawing showing the principal part structure as a 1st modification in the imaging lens shown in FIG. It is sectional drawing showing the principal part structure as a 2nd modification in the imaging lens shown in FIG. It is sectional drawing showing the principal part structure as a 3rd modification in the imaging lens shown in FIG. It is sectional drawing showing the principal part structure as a 4th modification in the imaging lens shown in FIG.

Explanation of symbols

L1 to L3: first to third lenses, CG: cover glass, Si: i-th lens surface from the object side, Z1: optical axis, 10: translucent region, 20: light shielding region, 30: step.

Claims (5)

An imaging lens composed of a single lens or a plurality of lenses,
At least one lens surface of the single lens or the plurality of lenses,
A translucent region that transmits the incident luminous flux;
A light blocking area that blocks incident light flux;
A step in a normal direction of the lens surface that defines a boundary between the light transmitting region and the light shielding region,
An imaging lens, wherein a coating film having a light shielding property is formed on the entire light shielding region with the step as a boundary. The entire light shielding region of the lens surface has a shape protruding in a normal direction or a depressed shape with respect to the lens surface of the light transmitting region with the step as a boundary. The imaging lens described. A convex portion or a recessed portion protruding in a normal direction to the lens surface of the light transmitting region is formed in a part of the light shielding region of the lens surface, and the step is formed by the convex portion or the recess. The imaging lens according to claim 1, wherein the imaging lens is provided. The imaging lens according to any one of claims 1 to 3, wherein the light shielding region functions as an aperture stop. A method of manufacturing a lens having a light-transmitting region that transmits an incident light beam and a light-shielding region that blocks the incident light beam,
After providing a step defining a boundary between the light transmitting region and the light shielding region in the normal direction of the lens surface, a coating film having a light shielding property is formed on the entire light shielding region with the step as a boundary. A method for producing a lens characterized by the above.

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